stripper clips are the way to go. I have an SKS with a 10 round fixed magazine, and the strippers make it really easy to load. using strippers for the AR is a little more difficult because the magazines don't have a stripper guide like the SKS.
Stripper Guide is on the bolt carrier
Making it easy to load the magazine
The AR magazine doesn't have one which makes it a little more difficult to load with stripper clips. It doesn't take long to fully load it though. I have used those "speed" loaders before, they are nice, but I guess I'm too cheap to buy one. Oh well, as long as I get to shoot I don't care